This application claims the priority of German Document No.: 103 07 858.4-25, filed Feb. 25, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a dismountable, that is, transportable bridge for a mobile use. Certain preferred embodiments of the invention relate to a dismountable bridge, having two track carriers which, viewed in a longitudinal direction of the bridge, are divided into several identical modules, the two tack carriers each being spanned by and being suspended at a vault, the vaults being divided into several modules in the longitudinal direction of the bridge, the vaults being adapted in their modular division to the modular division of the track carriers, the vaults and the track carriers being equipped at their ends with ends pieces.
When transportable bridges are used, they should correspond to the required span as well as to the required load, so that no excessive quantities of material have to be transported over long distances. This means that, by means of their construction, transportable bridges should adapt themselves to the obstacle and to the load. This is particularly important when the bridges are to reach their usage destination per air freight.
Several modular bridge concepts are known for adapting mobile bridges to the required load:
Double-Walled Construction
Here, two track carriers are arranged parallel side-by-side on both sides of a bridge. This solution is not mass-optimal because the moments of inertia of the two parallel carriers only add up, and so do their masses.
Double-Deck Construction
Here, two track carriers are arranged above one another on both sides of the bridge. Although the moment of inertia rises with twice the track carrier height, the bottom chord of the top track carrier as well as the top chord of the bottom track carrier come to be situated close to the neutral axis, contributing no longer to the overall bearing capacity, and thereby represent a “dead mass”.
Trussing
In this case, the two track carriers are trussed by means of a strut frame with one or more posts, which also contains the possibility of a prestressing. Disadvantages: The space required for the trussing below the bridge girder is not always available. In addition, the adjusted prestress has to be ensured for the entire duration of the usage.
Vertically Adjustable Structure (DE 38 14 502 A1 (Corresponding U.S. Pat. No. 5,042,101)
Here, longitudinally adjustable frame members permit the adaptation of the track carrier height to the intended load, so that approximately always the same member forces occur. Disadvantage: The bearing structure of the bridge becomes a mechanism which has to be actively adjusted or regulated.
In Austrian Patent Document AT 145 895, a bridge of the above-mentioned type is described in the case of which the track carriers are each spanned by a vault and are suspended at the latter. In the longitudinal direction of the bridge, the track carriers as well as the vaults are divided into several modules. The track carrier modules have a mutually identical construction, while the vault modules, as a function of their position along the longitudinal direction of the bridge and of the local slope existing there with respect to the horizonal line, have different lengths. In the case of this bridge, a reduction of the span takes place in that, symmetrically to the bridge center, two bridge modules are removed which each consist of the track carrier module, the vault module and the suspension rod. In a bridge shortened in this manner, the pertaining vault module in each bridge module maintains its original slope in each bridge module; only the length of the pertaining suspension rod of this and further bridge modules has to be adapted. Because of this construction principle, the lengths, measured in the direction of the bridge span, of the vaults and the track carriers always coincide for any possible bridge length. However, in the case of this bridge, a larger number of vault modules of different lengths has to be present. This complicates the transport and the construction and leads to relatively long construction times of the bridge. If one of the bridge modules is lost, it cannot easily be replaced by another. These characteristics are not tolerable for military bridges which can be transported by air and in the case of which rapidity during the transport and construction as well as robustness are the most important features.
It is an object of the present invention to provide a modular-construction mobile bridge which, while the above-mentioned disadvantages of the state of the art are avoided, is characterized by a high variability and can be flexibly adapted to the obstacle and the load.
This object is achieved according to certain preferred embodiments of the invention by providing a dismountable bridge, having two track carriers which, viewed in a longitudinal direction of the bridge, are divided into several identical modules, the two track carriers each being spanned by and being suspended at a vault, the vaults being divided into several modules in the longitudinal direction of the bridge, the vaults being adapted in their modular division to the modular division of the track carriers, the vaults and the track carriers being equipped at their ends with end pieces, wherein the modules of the vaults have mutually identical constructions, wherein the end pieces of the vaults are connected in a torque-resistant manner with end pieces of the respective track carriers, and wherein the end pieces are constructed such that they are capable of compensating the length differences between the track carriers and the vaults in the case of different bridge lengths.
Advantageous features of respective various preferred embodiments of the invention are described herein and in the claims.
According to certain preferred embodiments of the invention, the load bearing capacity of the bridge track carriers is increased by two vaults which span the bridge and at which the bridge track carriers are suspended, for example, by way of tension members. Instead of tension members, arbitrary prestressable elements, particularly flexible belts, bands (for example, made of textile materials) can be used.
According to certain preferred embodiments of the invention, in their modular division, the two vaults are adapted to the division of the bridge track carriers. In this case, the individual modules of the vaults are mutually constructionally identical and particularly have the same length. Likewise, the individual modules of the track carriers are mutually constructionally identical and have the same length.
At their ends, the vaults and track carriers are in each case equipped with end pieces, the end pieces of the vaults being connected with the end pieces of the respective track carriers in a moment-resistant or torque-resistant manner, and the end pieces are constructed such that they are capable of balancing length differences (measure in the bridge span) between the track carriers and the vaults in the case of different bridge lengths.
As a result of the modular construction, the vault structure also adapts to the bridge length. Since the height of the vault is approximately proportional to the span, the loading of the individual components does not change very much over the span of the bridge.
Typical spans of the bridge according to the invention are in the range of up to approximately 30 m.
Advantages of Certain Preferred Embodiments of the Invention
The dismountable bridge can be stored in a volume-optimal and therefore air-transportable manner.
According to certain preferred embodiments of the invention, the vaults and track carriers are each constructed of identical modules, which significantly increase the variability of the bridge when it is in use. Damaged or lost components an be replaced by other constructionally identical components.
Bridge girders of a lower bearing capacity can be reinforced by means of the vaulting.
The effectiveness of the reinforcement is approximately proportional to the span of the bridge.
The reinforcement extends upward where, as a rule, space is always available. A collision with an obstacle can therefore be prevented in every case.
The vaulting is mounted on the already laid bridge and can also be demounted at a laid bridge without building back the entire bridge; that is,                the weight of the vaulting of the bridge does not have to be laid, for example, in a free projection;        defective parts can be exchanged without building back the bridge.        
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.